Eosinophils are white blood cells of the granulocytic lineage. Their normal function appears to be combating parasitic infections, particularly helminthic infections. However, their accumulation in tissues, a condition referred to as eosinophilia, is also associated with several disease states, most notably asthma, e.g. Frigas et al, J. Allergy and Clinical Immunol., Vol. 77, pgs. 527-537 (1986); Gleich, Hospital Practice (Mar. 15, 1988); and Weller, J. Allergy and Clinical Immunol., Vol. 73, pgs. 1-10 (1984). It is believed that the damage to the epithelial lining of the bronchial passages in severe asthmatic attacks is largely caused by the compounds released by degranulating eosinophils.
Currently glucocorticoid steroids are the most effective drugs for treating the acute effects of allergic diseases, such as asthma. However, prolonged steroid treatment is associated with many deleterious side effects, Goodman and Gillman, The Pharmacological Basis of Therapeutics, 6th Ed. (MacMillan Publishing Company, New York, 1980). Moreover, the steroids apparently do not affect the production or accumulation of granulocytic cells, such as eosinophils, in the afflicted tissues. The availability of alternative or complementary approaches to the treatment of disorders associated with eosinophilia would have important clinical utility.